Download Tuesday5/10

The Structure of a DNA Molecule:
Semiconservative
DNA
Replication:
new
old
old
Catching &
Repairing Mistakes
DNA Polymerases err at
a rate of 1/10,000 base
pairs.
“Proofreading”
reduces the error rate
to 1/1 billion base pairs.
Cells can repair many
errors; Humans have
130 known DNA repair
enzymes!
The ability to repair
damaged DNA is critical to
long-term survival.
Individuals with xeroderma
pigmentosum produce
defective repair enzymes.
Without these repair
enzymes, mutated DNA in
skin cells (UV) is not
repaired, leading to skin
cancers.
Next…
What do cells
DO with their
DNA.??
Getting From a Gene to a Polypeptide
1. TRANSCRIPTION:
transcribing DNA into RNA
2. TRANSLATION:
translating RNA into an
amino acid
sequence
RNA vs DNA
In order to
translate DNA
(RNA) you
must first crack
the genetic
“code”!
A group of three
bases (a
codon) codes
for a particular
amino acid.
Arabidopsis thaliana C24
wild type (left) and
transformed (GFP; right)
Tobacco plant expressing a
firefly gene (luciferase)
Herman, at right, is the first transgenic
dairy animal engineered to make the
human milk protein, lactoferrin, which
is an antibacterial protein that can
be used to treat immunosuppressed
patients and could be incorporated
into infant formula.
TRANSCRIPTION
occurs in 3 Steps:
1.  Initiation
(promoter)
2.  Elongation (RNA
Polymerase)
and
3.  Termination
Let’s Watch:
http://www.dnai.org/
lesson/go/19436/15510
1. Ends are
capped and
tailed.
2. INTRONS cut
out.
RIBOSOMES are
Enzymes that
“Read” the mRNA
tRNA’s (transfer
RNA’s) deliver the
correct amino
acid specified by
the mRNA
You Try: Part 1
You Try: Part 2
The Effects: